Fuel supply system for internal combustion engines with improved filling of the fuel line

ABSTRACT

The invention proposes a fuel supply system for internal combustion engines, having a fuel tank ( 1 ) and a fuel reservoir ( 5 ) disposed therein, having a fuel pump ( 11 ), which drives one or more jet pumps ( 13 ), each by means of a supply line ( 21 ), the jet pumps ( 13 ) in turn filling the fuel reservoir ( 5 ) with fuel from the fuel tank ( 1 ). There is also a fuel line ( 7 ), which hydraulically connects the fuel reservoir ( 5 ) to the engine. During the starting of the engine, the fuel pump ( 11 ) feeds fuel into the fuel line ( 7 ), thus improving the starting behavior of the engine.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 35 USC 371 application of PCT/DE 01/00312 filed onJan. 26, 2001.

BACKGROUND OF THE INVENTION

1. Field of the Invention

2. Description of the Prior Art

The invention is based on a fuel supply system for internal combustionengines, having a fuel tank and a fuel reservoir disposed therein,having means for filling the fuel reservoir with fuel from the tank, andhaving a fuel line that hydraulically connects the fuel reservoir to theinternal combustion engine.

Fuel supply systems of this kind are known. The purpose of the fuelreservoir is to assure that the fuel line, which extends into the fuelsupply system, aspirates fuel and not air for as long as possible. Thisis particularly important when the tank is near empty and/or when thevehicle is subject to powerful lateral accelerations so that thecontents of the fuel tank are pushed to the side. This effect isachieved in that the fuel reservoir has a relatively small base and aheight that corresponds approximately to the height of the fuel tank sothat only a relatively small volume of fuel is required to fill the fuelreservoir. This fuel volume is supplied to the fuel reservoir by one ormore fuel pumps, which aspirate fuel from the low point(s) of the fueltank. In order to reduce costs, an electric fuel pump is usuallyprovided inside the fuel reservoir and drives one or more jet pumpsdisposed in the low point(s) of the fuel tank; the jet pumps supply fuelinto the fuel reservoir. This arrangement obviates the need to providean electric fuel pump in every low point of the fuel tank, which wouldbe expensive and prone to malfunction.

In many internal combustion engines, the fuel is supplied by means of afuel line, which aspirates in a fuel supply system. The fuel isdelivered by a fuel-supply pump directly coupled to the engine. Thismeans that at low speeds of the engine, the fuel-supply pump only has avery low delivery capacity. As a result, the fuel-supply pump aspirateslittle or no fuel from the fuel supply system, which has adisadvantageous effect on the starting behavior of the engine. This alsoplaces heavy loads on the starter and starter battery. This operatingbehavior is particularly problematic when the fuel tank has been run outof gas, when the vehicle is first filled with fuel at the manufacturer,or at low outside temperatures when the performance of the starterbattery is reduced.

The object of the invention is to produce a fuel supply system forinternal combustion engines, which improves the starting behavior of theengine even under unfavorable conditions and consequently contributes toreducing the strain on the starter battery and the starter.

This object is attained according to the invention by means of a fuelsupply system for internal combustion engines having a fuel tank and afuel reservoir disposed therein, having means for filling the fuelreservoir with fuel from the fuel tank, and having a fuel line providinga fluid connection between the fuel reservoir and the engine, where themeans for filling the fuel reservoir at least sometimes supply fuel intothe fuel line.

SUMMARY OF THE INVENTION

In accordance with this invention, the supplying of fuel to the internalcombustion engine does not depend solely on the delivery capacity of thefuel-supply pump of the engine; instead, particularly when starting theengine, the means for filling the fuel reservoir can also be used tosupply fuel into the fuel line. This assures that fuel travels throughthe fuel line to the engine in an extremely short time and consequentlyimproves its starting behavior. Since in essence, only already existingcomponents of the fuel supply system are used, the costs for thismeasure are very low, which is of particular significance in vehiclesthat are mass-produced.

In one embodiment of the invention, a connecting line is providedbetween the means for filling the fuel reservoir and fuel line so thatthe fuel quantity supplied by the means for filling the fuel reservoircan be fed into the fuel line regardless of location and canconsequently be adapted to the structural conditions at hand.

In one embodiment of the invention, a pressure-holding valve is disposedbetween the means for filling the fuel reservoir and fuel line so thatthe working pressure of the jet pumps is always assured. This alsoassures that the fuel reservoir is filled with fuel from the fuel tankat all times. The pressure holding valve also at least partiallyprevents the fuel line from emptying out during times when the engine isnot running.

In another embodiment of the invention, a throttle is provided betweenthe means for filling the fuel reservoir and fuel line, thus permittinga definite distribution of the fuel flow delivered by the fuel pump tothe jet pumps and the fuel line.

In another advantageous embodiment of the invention, a throttle and acheck valve are provided between the means for filling the fuelreservoir and the fuel line so that on the one hand, a definitedistribution of the fuel flow delivered by the fuel pump is possible andon the other hand, the fuel line is prevented from emptying out duringtimes when the engine is not running.

Another embodiment of the invention provides that a 3/2-portdirectional-control valve is disposed between the means for filling thefuel reservoir and the fuel line, that in its first switched position,the directional-control valve connects the means for filling the fuelreservoir to the fuel line and in its second switched position, the3/2-port directional-control valve connects the means for filling thefuel reservoir to the jet pump(s) so that when needed, the entiredelivery capacity of the fuel pump is available for filling the fuelline, which achieves a further improvement in the starting behavior ofthe engine. On the other hand, the entire delivery capacity of the fuelpump can also be used for filling the fuel reservoir.

Another embodiment of the invention provides that a 3/3-portdirectional-control valve is disposed between the means for filling thefuel reservoir and the fuel line, that in its first switched position,the 3/3-port directional-control valve connects the means for fillingthe fuel reservoir to the fuel line, that in its second switchedposition, the 3/3-port directional-control valve connects the means forfilling the fuel reservoir to the fuel line and the jet pump(s), andthat in its third switched position, the 3/3-port directional-controlvalve connects the means for filling the fuel reservoir to the jetpump(s). This embodiment assures that the fuel pump rapidly fills thefuel line; on the other hand, even when the second switched position isreached, the jet pumps in the fuel tank are also driven, thus preventinga reduction of the fuel level in the fuel reservoir.

Another embodiment of the invention provides that the 3/2-portdirectional-control valve or the 3/2-port directional-control valve isbrought into its first switched position in a spring-loaded fashion andthat the 2/3-port directional-control valve or the 3/3-portdirectional-control valve is brought into the second and possibly thirdswitched position, counter to a spring force, through the use of fuelfrom the means for filling the fuel reservoir. This arrangement assuresthat after each time that the engine—and therefore also the fuel pump inthe fuel supply system—is not in use, the 3/2-port directional-controlvalve or the 3/3-port directional-control valve is brought into itsfirst switched position so that with the start of delivery by the fuelpump, the fuel line is filled immediately. Because the fuel delivered bythe fuel pump actuates the directional-control valves, depending on thepressure level of the fuel delivered by the fuel pump, the spring force,and a throttle that is possibly provided, these directional-controlvalves travel into the second and possibly third switched position aftera particular period of time. This assures that the fuel pump drives thejet pumps shortly after the beginning of fuel delivery and consequentlythe fuel reservoir is also filled.

Another embodiment of the invention provides that the fill level of thefuel reservoir is maintained at least at the fill level of the tank,independent of the means for filling the fuel reservoir so that the fuelline and the fuel pump never aspirate air and on the other hand, acontinuous operation of the fuel pump can be avoided. This permits thefuel pump to be designed for a shorter service life, which contributesto reducing costs and to reducing the amount of energy required to drivethe fuel pump.

Another embodiment of the invention provides that the means for fillingthe fuel reservoir include an electric fuel pump so that the means forfilling the fuel reservoir are inexpensive and easy to activate.

Another embodiment of the invention provides that the fuel pump drivesat least one jet pump disposed in the vicinity of the low point(s) ofthe fuel tank in the installation position and that the jet pump(s)feed(s) fuel into the fuel reservoir so that all of the fuel in the fueltank can be fed into the fuel reservoir in a simple manner.

In another embodiment of the invention, the fuel line has a check valve,which prevents the fuel line from emptying out when the engine is not inuse.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages and advantageous embodiments of the invention ensuefrom the following detailed description, taken in conjunction with thedrawings, in which:

FIG. 1 shows a first exemplary embodiment of a fuel supply systemaccording to the invention, with a pressure-holding valve;

FIG. 2 shows a second exemplary embodiment of a fuel supply systemaccording to the invention, with a throttle;

FIG. 3 shows a third exemplary embodiment of a fuel supply systemaccording to the invention, with a throttle and a check valve;

FIG. 4 shows a fourth exemplary embodiment of a fuel supply systemaccording to the invention, with a 3/3-port directional-control valve ina first switched position;

FIG. 5 shows the exemplary embodiment according to FIG. 4 in a secondswitched position;

FIG. 6 shows the exemplary embodiment according to FIG. 4 in a thirdswitched position;

FIG. 6A shows the system of FIG. 4, with a 3/2-port directional-controlvalve in a switched position corresponding generally to/the thirdswitched position, and

FIG. 7 shows the characteristic curves of the exemplary embodimentsaccording to FIGS. 1 to 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Components that correspond to those in subsequent figures are providedwith the same reference numerals; explanations that are given inconjunction with one figure correspondingly apply to the other figures.

FIG. 1 schematically depicts a first exemplary embodiment of a fuelsupply system according to the invention, with a pressure-holding valve.A fuel tank 1, the upper half of which is not shown in FIG. 1, has twolow points 3. A fuel reservoir 5 that is open at the top is disposed inthe fuel tank 1.

The internal combustion engine, not shown, and the associatedfuel-supply pump feeds fuel from the fuel reservoir 5 to the engine bymeans of a fuel line 7 that extends into the fuel reservoir 5. In orderto prevent the fuel line 7 from emptying out, a first check valve 9 isprovided at its end.

The purpose of the fuel reservoir 5 is to assure that the fuel line 7aspirates fuel and not air for as long as possible, even when the levelof fuel in the fuel tank 1 is low. The fuel reservoir 5 has a muchsmaller base than the base of the tank 1 and its wall is approximatelythe same height as the fuel tank 1. This makes it possible to achieve ahigh fill level in the fuel reservoir 5 with a small quantity of fueland to consequently assure that the fuel line 7 aspirates fuel for aslong as possible.

The fuel reservoir 5 is filled by means which are essentially comprisedof a fuel pump 11 and a jet pump 13 in each low point 3 of the fuel tank1. One of the jet pumps 13 feeds fuel into the lower region of the fuelreservoir 5 and has a second check valve 15, which prevents fuel fromflowing back out of the fuel reservoir 5 into the tank 1. When the fuelpump 11 is switched off, the fuel reservoir 5 is filled by means of thecheck valve 15, as a result of which the fill level in the fuelreservoir 5 is at least approximately the same as the fill level in thefuel tank 1. The other jet pump 13 feeds over the upper rim of the fuelreservoir 5 so that no check valve is required in it.

The fuel tank 1 is fed by a fuel return 17, which conveys excess fuelback to the fuel tank 1. The fuel pump 11 aspirates fuel from the fuelreservoir 5 by means of a preliminary filter 19 and feeds it via supplylines 21 to the jet pumps 13 and via a connecting line 23 into the fuelline 7. In order to assure the pressure required for the jet pumps 13,the connecting line 23 is provided with an overflow valve 25, which isdesigned so that it only opens when the required working pressure of thejet pumps 13 has been achieved. As soon as the overflow valve 25 opens,part of the fuel delivered by the fuel pump 11 is fed via the connectingline 23 into the fuel line 7. The first check valve 9 in the fuel line 7also prevents fuel from traveling out of the connecting line 23 and backinto the fuel reservoir 5. This arrangement assures that the fuel line 7is filled with fuel in an extremely short time and consequently permitsthe engine to be started.

FIG. 7 shows a graph of the characteristic curve of this exemplaryembodiment according to the invention. The pressure difference in bar isplotted on the abscissa 27, while the ordinate 29 shows the flow rate inliters per hour. The characteristic curve of the first exemplaryembodiment is labeled 31. It shows that only after reaching a pressuredifference of 0.3 bar does the overflow valve 25 open and the flow rate,beginning from zero, rises in a linear fashion with the increasingpressure difference.

FIG. 2 shows a second exemplary embodiment of a fuel supply systemaccording to the invention, which in lieu of a pressure-holding valve,has a throttle 33 in the connecting line 23. This produces acharacteristic curve that differs from that of the first exemplaryembodiment. The characteristic curves 35 and 37 for two differentthrottle cross sections are plotted in FIG. 7. They show that even witha very slight pressure difference, fuel is already being fed into theconnecting line 23 so that the fuel line 7 is filled rapidly. Underunfavorable conditions, the pressure that builds up on the pressure sideof the fuel pump 11 can be insufficient to assure the function of thejet pumps 13.

In order to prevent this, in an exemplary embodiment according to FIG.3, a throttle 33 is combined with a third check valve 39. FIG. 7 showsthe characteristic curve 41 of the check valve 39. It shows that when acertain pressure difference is reached, approximately 0.16 bar here, thethird check valve 39 opens and the flow rate rises very sharply withincreasing pressure difference. The combination of the characteristiccurves of the third check valve 39 and the throttle 33 is depicted inFIG. 7 as the characteristic curve 43. This curve shows that in thisexemplary embodiment, a certain amount of pressure difference is builtup first before the supply pump 11 feeds fuel into the fuel line 7. Thisimproves the operating conditions for the jet pumps 13 and also, thethird check valve 39 assures that when the engine is not in use, no fuelflows out of the fuel line 7, through the connecting line 23, and backinto the fuel reservoir 5. This assures that the fuel line 7 cannotempty out when the engine is not in use. This also contributes to animproved starting behavior of the internal combustion engine.

It goes without saying that the characteristic curves 31, 35, 37, 41,and 43 from FIG. 7 are only intended as examples of a concretecombination of the fuel pump 11, connecting line 23, overflow valve 25,throttle 33, and/or check valve 39. The quantitative course of theabove-mentioned characteristic curves can be varied greatly by changingone or more of these components; the qualitative course of thecharacteristic curves, however, is retained.

FIGS. 4, 5, and 6 show a fourth exemplary embodiment in differentoperating states. The fuel line 7 has a fuel filter 45 and a fueldelivery pump 47. The fuel fed from the fuel reservoir 5 by the fuelpump 11 is controlled by means of a 3/3-port directional-control valve49, which is shown in a first switched position. The 3/3-portdirectional-control valve 49 has a first connection 51, which connectsthe fuel pump 11 to the 3/3-port directional-control valve 49. A secondconnection of the 3/3-port directional-control valve 49 is connected tothe connecting line 23, while the third connection is connected to thesupply line 21.

The 3/3-port directional-control valve has a piston 53. This piston 53has a connecting bore with a throttle 55, which connects a first chamber57 of the 3/3-port directional-control valve 49 to a second chamber 59.A third chamber 61 contains a spring 63, which always brings the3/3-port directional-control valve into the first switched positionshown in FIG. 4 when the fuel pump 11 is inoperative.

As soon as the fuel pump 11 is activated, it feeds into the firstchamber 57 of the 3/3-port directional-control valve. Since in thisswitched position, the connecting line 23 is connected to the firstchamber 57, the fuel pump 11 feeds into the fuel line 7. A part of theflow stream of the fuel pump 11 travels through the connecting bore withthe throttle 55 in the piston 53, and into the second chamber 59,causing the piston 53 to move toward the spring 63, counter to the forceof the spring 63.

FIG. 5 shows the fourth exemplary embodiment in a second switchedposition. The piston 53 is positioned so that the chamber 57 ishydraulically connected to both the connecting line 23 and the supplyline 21. In this position, the fuel pump 11 supplies fuel to both thefuel line 7 and the jet pumps 13.

FIG. 6 shows the third switched position of the 3/3-portdirectional-control valve. In this switched position, the fuel pump 11only feeds into the supply line 21 and not into the connecting line 23.This means that the entire output of the fuel pump 11 is fed to the jetpumps 13.

FIG. 6 A shows a modification in which a 3/2-port directional-controlvalve is used in place of the 3/3-port directional-control valve. Inthis embodiment, the line 23 is closed before the line 21 is opened sothat the pump feeds only to line 21.

In this fourth exemplary embodiment, the fuel line 7 is filled asrapidly as possible and at the same time, the jet pumps 13 are driven assoon as possible. As a result, this produces a very favorable startingbehavior of the engine, not shown, and it is possible for the fuel pump11 to be small since it only has to continuously operate to supply thejet pumps 13. Optionally, a throttle 65 can be provided in theconnecting line 23, which results in the fact that the fuel flow in theconnecting line 23 is reduced and consequently, a greater portion of thefuel flow delivered by the fuel pump 11 flows through the connectingbore 55 into the second chamber 59. This increases the speed with whichthe piston 53 moves from the first switched position into the third.

All of features shown in the drawings, the specifications, and theclaims can be essential to the invention either individually or inarbitrary combinations with one another.

1. A fuel supply system for internal combustion engines, comprising, afuel tank (1) and a fuel reservoir (5) disposed therein, means (11, 13,21) for filling the fuel reservoir (5) with fuel from the fuel tank (1),and a fuel line (7) that hydraulically connects the fuel reservoir (5)to an engine, the means (11, 13, 21) for filling the fuel reservoir (5)feeding fuel into the fuel line (7) at least part of the time duringoperation further comprising a 3/2-port directional-control valvedisposed between the means (11, 13, 21) for filling the fuel reservoir(5) and the fuel line (7), the 3/2-port directional-control valve in itsfirst switched position connecting the means (11, 13, 21) for fillingthe fuel reservoir (5) to the fuel line (7), and in its second switchedposition, the 3/2-port directional-control valve connecting the means(11, 13, 21) for filling the fuel reservoir (5) to the jet pump(s) (13).2. The fuel supply system according to claim 1, further comprising aconnecting line (23) disposed between the means (11, 13, 21) for fillingthe fuel reservoir (5) and the fuel line (7).
 3. The fuel supply systemaccording to claim 1, further comprising an overflow valve (25) disposedbetween the means (11, 13, 21) for filling the fuel reservoir (5) andthe fuel line (7).
 4. The fuel supply system according to claim 2,further comprising an overflow valve (25) disposed between the means(11, 13, 21) for filling the fuel reservoir (5) and the fuel line (7).5. The fuel supply system according to claim 1, further comprising athrottle (33) disposed between the means (11, 13, 21) for filling thefuel reservoir (5) and the fuel line (7).
 6. The fuel supply systemaccording to claim 2, further comprising a throttle (33) disposedbetween the means (11, 13, 21) for filling the fuel reservoir (5) andthe fuel line (7).
 7. The fuel supply system according to claim 3,further comprising a throttle (33) disposed between the means (11, 13,21) for filling the fuel reservoir (5) and the fuel line (7).
 8. Thefuel supply system according to claim 1, further comprising a throttle(33) and a check valve (39) disposed between the means (11, 13, 21) forfilling the fuel reservoir (5) and the fuel line (7).
 9. The fuel supplysystem according to claim 2, further comprising a throttle (33) and acheck valve (39) disposed between the means (11, 13, 21) for filling thefuel reservoir (5) and the fuel line (7).
 10. The fuel supply systemaccording to claim 3, further comprising a throttle (33) and a checkvalve (39) disposed between the means (11, 13, 21) for filling the fuelreservoir (5) and the fuel line (7).
 11. The fuel supply systemaccording to claim 5, further comprising a throttle (33) and a checkvalve (39) disposed between the means (11, 13, 21) for filling the fuelreservoir (5) and the fuel line (7).
 12. The fuel supply systemaccording to claim 2, further comprising a 3/2-port directional-controlvalve disposed between the means (11, 13, 21) for filling the fuelreservoir (5) and the fuel line (7), the 3/2-port directional-controlvalve in its first switched position connecting the means (11, 13, 21)for filling the fuel reservoir (5) to the fuel line (7), and in itssecond switched position, the 3/2-port directional-control valveconnecting the means (11, 13, 21) for filling the fuel reservoir (5) tothe jet pump(s) (13).
 13. The fuel supply system according to claim 2,further comprising a 3/3-port directional-control valve (49) disposedbetween the means (11, 13, 21) for filling the fuel reservoir (5) andthe fuel line (7), the 3/3-port directional-control valve (49) in itsfirst switched position connecting the means (11, 13, 21) for fillingthe fuel reservoir (5) to the fuel line (7), and in its second switchedposition, the 3/3-port directional-control valve (49) connecting themeans (11, 13, 21) for filling the fuel reservoir (50) to the fuel line(7) and the jet pump(s) (13), and that in its third switched position,the 3/3-port directional-control valve (49) connects the means (11, 13,21) for filling the fuel reservoir (5) to the jet pump(s) (13).
 14. Thefuel supply system according to claim 1, wherein the 3/2-portdirectional-control valve or the 3/3-port directional-control valve (49)is brought into its first switched position in a spring-loaded fashion,and wherein the 3/2-port directional-control valve or the 3/3-portdirectional-control valve (49) is brought into the second and possiblythird switched position, counter to a spring force, by fuel from themeans (11, 13, 21) for filling the fuel reservoir (5), which fuel actsas a working medium.
 15. The fuel supply system according to claim 1,wherein the fill level of the fuel reservoir (5) is maintained at leastat the fill level of the fuel tank (1), independent of the means (11,13, 21) for filling the fuel reservoir (5).
 16. The fuel supply systemaccording to claim 1, wherein the means (11, 13, 21) for filling thefuel reservoir (5) include an electric fuel pump (11).
 17. The fuelsupply system according to claim 16, wherein the fuel pump (11) drivesat least one jet pump (13) disposed in the vicinity of the low point(s)(3) of the fuel tank (1) in the installation position, and wherein thejet pump(s) (13) feed(s) the fuel into the fuel reservoir (5).
 18. Thefuel supply system according to claim 1, wherein the fuel line (7) has acheck valve (9).
 19. The fuel supply system according to claim 1,wherein the 3/2-port directional-control valve is brought into its firstswitched position in a spring-loaded fashion, and wherein the 3/2-portdirectional-control valve is brought into the second switched position,counter to a spring force, by fuel from the means (11, 13, 21) forfilling the fuel reservoir (5), which fuel acts as a working medium. 20.A fuel supply system for internal combustion engines, comprising. a fueltank (1) and a fuel reservoir (5) disposed therein, means (11, 13, 21)for filling the fuel reservoir (5) with fuel from the fuel tank (1), anda fuel line (7) that hydraulically connects the fuel reservoir (5) to anengine, the means (11, 13, 21) for filling the fuel reservoir (5)feeding fuel into the fuel line (7) at least part of the time duringoperation, further comprising a 3/3-port directional-control valve (49)disposed between the means (11, 13, 21) for filling the fuel reservoir(5) and the fuel line (7), the 3/3-port directional-control valve (49)in its first switched position connecting the means (11, 13, 21) forfilling the fuel reservoir (5) to the fuel line (7), and in its secondswitched position, the 3/3-port directional-control valve (49)connecting the means (11, 13, 21) for filling the fuel reservoir (50) tothe fuel line (7) and the jet pump(s) (13), and that in its thirdswitched position, the 3/3-port directional-control valve (49) connectsthe means (11, 13, 21) for filling the fuel reservoir (5) to the jetpump(s) (13).
 21. The fuel supply system according to claim 20, whereinthe the 3/3-port directional-control valve (49) is brought into itsfirst switched position in a spring-loaded fashion, and wherein the3/3-port directional-control valve (49) is brought into the second andpossibly third switched position, counter to a spring force, by fuelfrom the means (11, 13, 21) for filling the fuel reservoir (5), whichfuel acts as a working medium.